Method and apparatus for removing coatings from metals

ABSTRACT

Thermochemical procedure and equipment for the substantially airless stripping of organic base coatings from objects by volatilization of the coating material as immersed in a molten salt bath. The procedure is carried out in a shroud-like objectreceiving retort. This retort, when immersed at least in part at an open bottom thereof penetrating in said bath, is substantially sealed hermetically against entry of external atmospheric air to its interior. The bath is heated in a conventional pot by conventional immersion heating means; and the interior of the retort is conditioned during immersion, as by being placed and held under partial vacuum or by introducing an inert gas, to greatly reduce air content in the space therein above the bath, thus creating a nonoxidizing atmosphere. The retort is shown as being by preference sealed at its top by a removable gas tight cover. Volatilization continues for a relatively very brief time period, the resulting vapor product and possible gas arising to the conditioned retort space above the bath level. During this volatilizing period, or directly before and thereafter and with the retort still sealed and bottom-immersed in the bath, its interior above the salt level is evacuated, as by a vacuum pump. The volatilization vapor, minimal product of combustion, smoke and the like are piped in a closed system to conventional incinerator, filter and/or scrubber means prior to discharge to atmosphere. The retort is then unsealed and placed in position for rinsing and removal of the stripped object or objects therefrom.

Kemper Nov. 6, 1973 METHOD AND APPARATUS FOR REMOVING COATINGS FROMMETALS Primary Examiner-Morris O, Wolk Assistant Examiner-Tim HaganAttorneyFranklin E. Quale [57] ABSTRACT Thermochemical procedure andequipment for l the substantially airless stripping of organic basecoatings from objects by Volatilization of the coating material asimmersed in a molten salt bath. The procedure is carried out in ashroud-like object-receiving retort. This retort, when immersed at leastin part at an open bottom thereof penetrating in said bath, issubstantially sealed hermetically against entry of external atmosphericair to its interior. The bath is heated in a conventional pot byconventional immersion heating means; and the interior of the retort isconditioned during immersion, as by being placed and held under partialvacuum or by introducing an inert gas, to greatly reduce air content inthe space therein above the bath, thus creating a nonoxidizingatmosphere. The retort is 1 shown as being by preference sealed at itstop by a removable gas tight cover. Volatilization continues for a Irelatively very brief time period, the resulting vapor interior abovethe salt level is evacuated, as by a vaclO/l97l Wainer ..".134/19X 26Claims, 4 Drawing Figures valr METHOD AND APPARATUS FOR REMOVINGCOATINGS FROM METALS BACKGROUND OF THE INVENTION FIELD The method andequipment of the invention will find use, whether in a small,structurally simple embodiment such as is schematically illustratedherein or on a larger scale form for mass stripping of small or largeobjects, in a dip or spray coating department of a plant in which, forexample, periodic strippings to remove incrustations of paint fromconveyor work holders are in order. Such a build-up, for example,adversely affects the conductivity of a work holder which serves as anelectrode in'an electrostatic paint spray operation. An equally commonapplication will be in the stripping of work products supported by aforaminated carrier in a retort, as well as in the stripping of massiveobjects in which a special carrier is not used.

SUMMARY OF THE INVENTION As used industrially in the stripping fromworkpieces and the like of a large number and variety of varnishes,enamels, lacquers, synthetic resin compositions, and organicbase-coatings in general, it is a commonly accepted fact that, in orderto comply even reasonably well with existing atmospheric anti-pollutionlaws and ordinances, industrial stripping installations of thethermo-chemical salt bath volatilization type must employ an elaborateventilation system in order to vent from the plants stripping area thevoluminous vapors, gases, smoke and soot which have inescapably beenevolved. This necessarily must in turn be followed by a large scaleincineration, filtering and/or scrubbing of such vapor and/or gasproducts prior'to their discharge to the external atmosphere.

Other known volatilization-type systems, such as the fluidized bed type,do not employ a salt bath as such, but in none of them is an effort madeto conduct the operation in a substantially oxygen-free atmosphere.

Specifically in relation to a molten salt bath operation, despite allconventional attempts to seal the bath s enclosure against entry ofcombustion-supporting atmospheric air prior to and during stripping, itinevitably occurs at necessary access openings, and in relatively largevolume, all things considered. The result is an extensive and violentcombustion of the volatilized organic base coating materials in thestripping pot zone, with attendant generation in a major degree of sootand other contaminants, in turn calling for resort to the extensive,expensive and space-consuming gas handling and disposal systemheretofore thought unavoidable.

By contrast, the method and equipment of the present invention, whiletherrnochemically relying as before upon the principle of vaporizationof organic constituents of the coating, also ordinarily to a degree onan ultimate incineration and/or scrubbing of the product ofvolatilization, operate in a manner to vastly diminish in all respectsthe size, complexity and expense of the installation. Needless to say,to the extent that the method and apparatus simplify a solution to aserious atmospheric problem they are well attuned to ecological aimswhich increasingly occupy the attention of the public.

Typically, the objects to be stripped, as carried in a foraminatecontainer appropriately supported within and from the top of ashroud-like vaporization retort, open at its bottom, are immersed in amolten salt bath of the stripping pot, but prior to this immersion, theinterior of the retort is tightly sealed from the external atmosphere,which may be readily accomplished in view of the relatively small sizeof the retort, particularly as herein shown. In being thus immersed inthe bath (which typically may be a mixture of sodium hydroxide andsodium nitrate or alkaline nitrates), the molten material of said bathincreasingly enters the retort at its open bottom; however, well beforethe work to be stripped becomes immersed the air space in the retortabove the level of the bath is either reduced to a substantiallysub-atmospheric pressure or has introduced into this space a lowpressure non-combustible 'gas, such as carbon dioxide or nitrogen.Likewise, in some cases the process may well tolerate the presence of asmall volume of air and resultant small oxidationat the outset andconclusion of the operation.

Further pursuant to the invention, and after volatilization for anappropriate time interval at an appropriate immersion bath temperature,the products of the volatilization, including vapor and whatever smallamount of gas and smoke that have been generated, and voided from theretort prior to opening the latter or other exposure of its interior,such as for removal of the container and its stripped content. Theconditioning of the retorts interior, as under the instanced vacuum, maybe done once per cycle under valve control, only at the commencement ofa stripping cycle, but is preferably continued throughout the durationof the cycle, i.e., a continuous removal of the products of vaporizationduring their continued generation from within the salt bath. Moregenerally stated, and more important, the understanding will be that theinvention contemplates a hermetic sealing of the zone above the bath.against the entry of atmospheric air during the stripping cycle. This,it will be noted, is the antithesis of operations and procedures of thepresent day, in which there is an inevitable fan or blower introductionof a large volume of air as an incident to the disposing of products ofvaporization, and an equally inescapable discharge of a large percentageof such products to pollute the atmosphere. This contrasts with thewholly sealed nature of the system disclosed herein, commencing at theretort and ending at the discharge end of an incinerator or scrubber. A

While the equipment, as herein illustrated and later specificallydescribed, involves the use of a vaporconfining retort at leastperiodically sealed at its top and periodically immersed along with workobjects housed therein and to be volatilization-stripped in the saltbath, the invention also contemplates a continued fixed immersion of theretort within the bath, the molten content of the latter desiredlyentering the retort through an open retort bottom or some other immersedarea. In one respect this fixed arrangement presents an advantage inpoint of eliminating repeated relative coolings and reheatings of theretort proper.

Similarly, the equipment as here shown and det scribed features a coverwhich is removable from the retorts top, being hermetically sealed tothe latter during the stripping cycle and carrying certainretortconditioning fittings. However, the cover need not necessarily beremovable from the retort, other provisions for removing the work or itscontainer from the retort and for conditioning the retort interior beingobviously practical.

In general, the invention essentially involves the separation oforganic-base substances from inorganic pieces or substances which areordinarily of metallic or metallic-base composition. However, use of theinvention is not confined to the separation of an organic substance froma three-dimensional object such as a workpiece. Further applications arecontemplated, for example, in the recovery, by a volatilizing separationtreatment, of a metallic component, whether the metal itself or a saltthereof, from a volatilizable organic part or substance, these organicand inorganic materials being present on or in an object as subjected tosuch treatment. Likewise, while the invention is shown and described interms of a batch procedure, continuing operations are contemplated inrespect to the voiding of the volatilized product, the conditioning ofthe retort and/or the placement and removal of the treated object.

It is further to be understood that while the equipment herein describedis, in the interest of simplicity, of a very elemental nature, any orall of the usual, and many times necessary, refinements present inindustrial stripping equipment may be incorporated. There are,forexample, sludge removal means, attendant or operator protectionmeans, bath agitation means and the like. However, it is, by the sametoken, to be noted that the method of the invention contemplates ashrouded hence quiescent bath, so that the mentioned agitation meanswill normally not be necessary.

Most importantly, a blower installation for ventilation of the zoneimmediately external of the volatilization stripping pot is or may benon-existent.

BRIEF DESCRIPTION OF THE DRAWING FIG. 1 is a very schematic perspectiveview showing the several components of the improved equipment, asdisposed in a relatively spread or vertically extended relationship toone another, comparable to that of FIG. 4, the retort cover and articlecontainer being shown in dotted line in FIG. 1 as swung to a position atone side for rinsing, container unloading and reloading;

FIG. 2 is a fragmentary view in side elevation, partially broken awayand in vertical cross-section on a diameter of the stripping pot andcover-sealed retort, illustrating the latter as fully immersed with thearticle container while stripping volatilization of the container-heldparts proceeds;

FIG. 3 is a view sectioned similarly to FIG. 2, but with the stillsealed retort and enclosed container in an elevated position followingthe volatilizing phase, the several means for elevating the retort andits cover to this vertically extended position also being better shown;and

FIG. 4 is a further similar view showing the retort as returneddownwardly into the pot for an ensuing cycle, the cover and articlecontainer being left elevated for rinsing, unloading and reloading, asswung to one side in the manner suggested in dotted line in FIG. 11.

DESCRIPTION OF A PREFERRED EMBODIMENT The equipment schematicallyillustrated in FIGS. 1-4, and generally designated by the referencenumeral 10, is preferred only in the sense that it represents a typicaland simple, if not generic or all-encompassing, illustration of theprocedural and structural principles of the invention. Thus, theapparatus 110 comprises an appropriately insulated pot, vat or tank 11which is shown as cylindrical in cross-section and fixedly mounted uponeither a floor or elevated support S. It is open at its top, throughwhich it may receive one or more conventional immersion heaters 12 ofeither the electrode or internally gas-fired type, although externalheating may be employed; and such heater means is conventionallycontrolled to maintain a salt bath B in the pot ill at a typical moltentemperature of, say, 900 F. However, temperatures as low as 300 F. andas high as 1,300 F. or above are contemplated; the composition andtemperature of bath B will, of course, vary in nature with the productand its coating to be stripped, and specifically as such constitute nopart of the present invention.

A cylindrical and vertically elongated, imperforatewalled shroud-likeretort l3, wholly open at its bottom 13', is mounted coaxially of thepot 11 in a manner to be described, being equipped at its top with anannular bead or flange 14 at which a mating circular and mildly domedcover 15 will have a hermetically sealed connection during thevolatilization phase of the method. This seal may be effected throughthe agency of an annular compressible gasket 15' interposed between theretort flange l4 and an inturned annular flange 15" of cover 15, as whenthe latter is vacuum drawn downwardly to compress gasket 15'. In thealternative the seal may be effected by knife edge or other knownequivalent means. The seal may also be maintained by positive clampingof the cover in place or by gravity alone.

In any case, it is of the essence of the invention that the access ofexternal atmospheric air into the interior of the shrouded retort 13during the volatilization phase, and preferably for short periods priorand subsequent thereto, be prevented. During the treatment in question,the retort is preferably lowered well down into the bath 18, its lowerexposed rim edge 13 being but slightly elevated above the floor of vat11. However, since it is only necessary to obtain a hydrostatic seal atthat rim, the immersion, though desirably, need not necessarily be sofully complete, thus enabling a retort of lesser axial length to beused.

For the purpose of thus immersedly lowering the retort l3 andsubsequently elevating it and its content, the invention illustrativelycontemplates the use of a horizontal support arm 16 fixed to andextending radially outwardly of a circular lift and lower collar 17underlying the retort flange 114. Said arm 16 is fixed at its outer endto the vertically acting plunger of a conventional pneumatic orhydraulic type cylinder 18 having pressure entry and exhaust connections19 adjacent its upper and lower ends. The cylinders plunger isdesignated 20.

Cylinder is is illustrated schematically as being received betweenparallel upright legs of a fixed upright guide frame 211. Such legs areof lesser and greater height, being therefore designated 21 and 21respectively; and the retorts radial support arm 16 is guided betweensaid legs for up and down movements of retort 13 on the axis of pot ii.

A generally similar, but differently operated, crossarm or cantileversupport is provided for the removable sealing cover 15 of the retort,i.e., one which will permit a suitable lateral swing of the cover fromits elevated solid line, retort-centered position of FIG. 1 to therinsing, unload and reload position appearing in dotted line in thatfigure. To this end, a radially extending cross arm 22 is schematicallysuggested as being secured to the top center of cover 15. The outer endof this arm is secured to the top of a vertically elongated guide rod 23which is mounted for vertically sliding action and limited turn inrelation to the legs 2H, 21" of guide frame 21, the rotational componentof arm 22 being in a horizontal plane above the shorter frame leg 21 Arod 23 which carries the arm is stably guided for vertical action in anupright supplemental bracket structure 24 which fixedly abuts a side ofthe retort guide frame 21.

An elongated flexible cable 25 is secured to arm 22 directly above thelatters radially outer connection to rod 23, the cable being trainedhorizontally outwardly and then downwardly about a pair of pulleys 26which are journalled on a top and side extension 27 of the taller retortguide leg 21 it being again noted that the shorter comparable leg'21'terminates at an elevation sufficiently beneath the fully raisedcover-hanging cross arm 22 to permit the swing of arm 22 indicated inFIG. ll. Cable 25 carries a cover-balancing counterweight 25'.

Referring to FIGS. 2, 3 and 4, a straight or spider-like cross piece 28is fixedly mounted within retort cover 15 to extend diametricallythereof; and piece 28 fixedly carries a depending hook 29, which servesas a support for the bail of a removable article container 30, shown asbeing of cylindrical cross-section. The wall of container 30 isplentifully perforated at 31, or otherwise meshed or foraminated topermit free access to and full immersion of articles to be stripped inthe portion of bath B which enters retort 13 from the latters openshroud bottom 13'.

Cover 15 is preferably equipped with a conventional automaticpressure-regulated vent fitting 33 at its top, through which anexcessive vapor and/or gas pressure in retort 13 during thevolatilization phase may be vented and/or forwarded externally, asthrough an appropriate line 34. More importantly, cover 15 carries afitting 35 at which an elongated flexible conduit or hose 36 has anairtight connection, the hose leading to a schematically shownmulti-port valve 37. This hose and valve will optionally connect fitting35, as through a line'35', to a'source of an inert gas such as CO or Nfor the low pressure charging of the sealed interior of retort 113. Thisis in one possible adaptation of the invention mentioned above. Inanother and preferred embodiment, valve 37 will connect through asuitable conduit 38 to a vacuum pump (not shown) for the evacuation ofthe retort interior prior to, during and shortly after volatilization,there being by preference,

appropriate passaging in the valve to break such vacuum aftervolatilization.

in accordance with the preferred vacuum-based procedure pursuant to theinvention, articles to be paint or coating-stripped are eitherindividually suspended from the hook 29 of retort coverlS, or are placedin the container or carrier 30, being similarly hook-suspended in thelatter. With the retort 13 in the fully lowered position of FIG. 2, orsufficiently lowered to liquid-seal its bottom rim 13', valve 37 isoperated to drop the pres sure beneath cover 15 and above the salt bathlevel, once the cover has been lowered onto the sealing bead or flange14 of the retort. External atmospheric pressure thus causes the cover tohave a hermetic seal atop the retort l3, preventing access of anyatmospheric air to the retort interior. Stripping volatilization nowoccurs for the contemplated limited time interval at the indicatedelevated salt bath temperature.

Assuming the evacuation of any significant air content above the saltbath level, as designated L in FIGS. 2, 3 and 4, the level will risesomewhat within retort 13, but in no significant degree sufficient toalter the extent of sub-atmospheric pressurization of the interior; andthe volatilization proceeds to termination without a sustainedaccumulation of any volume of vapor, gas or suspended matter in anydegree corresponding to the accumulation inevitable to result in theabsence of a seal of the retort against entry of external atmosphericair.

Upon completion of volatilization and stripping, valve 37 may beoperated to void the products of volatilization to the incinerator,filter and/or scrubber unit; but by preference the evacuation iscontinuously maintained, with continuous voiding of the primarilyvaporous product of volatilization as it arises, thus diminishing theload on a diminished scale incinerating and/or scrubbing adjunct orsystem.

The retort 13, with its cover 15 still sealed thereto, is now elevatedthrough the agency of the lift-lower cross arm 16 as powered by fluidpressure cylinder 18, to a position approximately as shown in FIG. 3,yet with the lower open rim 13 of the retort remaining beneath the levelof the bath B. The article container 30 is then well above the saltlevel in pot 11; and at any time in or prior to this phase the retortinterior may be deconditioned through valve 37, as by breaking thevacuum or alternatively discontinuing the inert gas supply.

Retort l3 alone is then restored downwardly to the fully loweredposition of MG. 4, ready for a next cycle of operation. Article carrieror container 30 and its stripped content remain in the counter weighted,cableelevated position of PEG. 4, to be swung laterally to the dottedline position of FIG. l for spray rinsing, emptying and recharging, thenreturn of the loaded cover to coaxiality with and seating on retort 13as described above.

I claim:

l. A method of removing coating material from an object, comprisingimmersing said object in a molten volatilization bath, creating andmaintaining a reduced oxygen atmosphere in a space above the level ofthe bath by evacuating said space, which space is sealed against entryof external air thereto when said object is so immersed, maintainingsaid immersion for a time period and at an elevated temperaturesufficient to cause volatilization of said coating material and escapeof the volitilization product to said space, and withdrawing the escapedproduct from the space.

2. A method of removing organic base coating material from an object,comprising disposing said object in a partially exposed but otherwisesealed retort, immersing the retort and the thus disposed object in amolten salt bath, with the object being substantially totally immersedand the retort at least sufficiently immersed that the partial exposurethereof is sealed by a portion of said bath, the bath being at atemperature sufficiently elevated to volatilize said material, creatingand maintaining a reduced oxygen atmosphere in a space in the thussealed retort above the level of said bath portion therein, maintainingsaid immersion for a time period sufficient to cause volatilization ofsaid coating material and escape of its volatilization product to saidspace, and voiding the escaped product from said space prior to removingthe object from the retort.

3. The method of claim 2, in which the volatilization product is voidedunder a condition of partial vacuum.

4. A method of removing coating material from an object, comprisingimmersing said object in a molten volatilization bath, creating andmaintaining a reduced oxygen atmosphere in a space above the level ofthe bath, which space is sealed against entry of external air theretowhen said object is so immersed, maintaining said immersion for a timeperiod and at an elevated temperature sufficient to cause volatilizationof said coating material and escape of the volatilization product tosaid space, and withdrawing the escaped product from the space in whichthe immersed object is disposed in a retort which is also at leastpartially immersed in the volatilization bath, being filled to apredetermined level with a portion of the bath in which the object isimmersed, the sealed space being in said retort and above saidpredetermined level therein.

5. The method of claim 1, in which said reduced oxygen atmosphere iscreated by placing said sealed space under a substantiallysub-atmospheric pressure.

6. The method of claim 2, in which said reduced oxygen atmosphere in theretort is created by placing said sealed space in the latter under asubstantially subatmospheric pressure.

7. The method of claim 4-, in which said reduced oxygen atmosphere inthe retort is created by placing said sealed space in the latter under asubstantially subatmospheric pressure.

8. The method of claim 2, in which said reduced oxygen atmosphere in theretort is created by introducing a normally substantially non-oxidizinggas into said sealed space of the retort.

9. The method of claim 4, in which said reduced oxygen atmosphere in theretort is created by introducing a normally substantially non-oxidizinggas into said sealed space of the retort.

10. The method of claim 1, in which the object is suspended during thevolatilizing immersion thereof in said retort portion of said bath.

lll. The method of claim 2, in which the object is suspended during thevolatilizing immersion thereof in said retort portion of said bath.

12. The method of claim 4, in which the object is suspended during thevolatilizing immersion thereof in the retort portion of said bath.

13. The method of claim 2, in which said bath portion enters the retortfrom the bottom of the latter as the object and retort become immersed,said sealed retort space to which the volatilization product escapesbeing at the top of the retort.

14. The method of claim 4 in which said bath portion enters the retortfrom the bottom of the latter as the object and retort become immersed,said sealed retort space to which the volatilization product escapesbeing at the top of the retort.

15. The method of claim 11, in which said bath portion enters the retortfrom the bottom of the latter as the object and retort become immersed,said sealed retort space to which the volatilization product escapesbeing at the top of the retort.

to. The method of claim 22, in which said bath portion enters the retortfrom the bottom of the latter as the object and retort become immersed,said sealed retort space to which the volatilization product escapesbeing at the top of the retort.

17. Apparatus for removing by volatilization a coating material from anobject, comprising an objectreceiving retort having means to seal theinterior thereof as at least partially immersed, along with an objectreceived therein, in a volatilizing bath, said retort having an exposedportion at which the bath enters the thus immersed retort, means formaintaining the bath at a temperature sufficiently elevated tovolatilize said material, means for creating a reduced oxygen atmospherein a space of the retort above the bath portion therein, thevolatilization product escaping to said space, and means for voidingsaid product from said space after volatilization.

18. The apparatus of claim 17, in which said retort I has an open bottomaffording said closed portion, and means sealing the top of the retortabove the level of the bath entering the same.

19. The apparatus of claim 17, in which said retort has an open bottomaffording said closed portion, and means releasably sealing the top ofthe retort above the level of the bath entering the same.

20. The apparatus of claim 119, in which said sealing means is a coverremovable from the remainder of the retort before and aftervolatilization, the cover being provided with a fitting-type connectionassisting in the creation of said reduced oxygen atmosphere.

211. The apparatus of claim 17, in which said retort has means forlowering and raising the same relative to the bath respectively beforeand after immersion of the retort.

22. The apparatus of claim 19, in which said retort has means forlowering and raising the same relative to the bath respectively beforeand after immersion of the retort.

23'. The apparatus of claim 17, in which said retort is in fixedrelation to the bath before, during and after immersion thereof.

24. A method of treating an object to separate organic and inorganicmaterials thereof as subjected to treatment, comprising immersing saidobject in a molten volatilization bath, creating and maintaining areduced oxygen atmosphere in a space above the level of the bath byevacuating said space, which space is sealed against entry of externaiair thereto when said object is so immersed, maintaining said immersionfor a time period and at an elevated temperature sufficient to causevolatiiization of the organic material, escape of the organicvolatilization product to said space and said separation of saidmaterials, and withdrawing the escaped product from the space.

25.. Apparatus for treating an object to separate organic and inorganicmaterials thereof as subjected to treatment, comprising anobject-receiving retort having means to seal the interior thereof asthus subjected, along with an object therein, to a volatilizingenvironment, means for maintaining said environment at a temperaturesufticiently elevated to volatilize said organic material, a vacuum pumpfor creating a reduced oxygen atmosphere in a space of the retortadjoining said atmosphere, the gaseous product of the organic materialescaping to said space, and means for voiding said product from saidspace.

26. Apparatus for treating an object to separate organic and inorganicmaterials thereof as subjected to treatment, comprising anobject-receiving retort having space of the retort above the baththerein, the gaseous product of the organic material separating from theinorganic material and escaping to said space, and means for voidingsaid product from said space.

2. A method of removing organic base coating material from an object,comprising disposing said object in a partially exposed but otherwisesealed retort, immersing the retort and the thus disposed object in amolten salt bath, with the object being substantially totally immersedand the retort at least sufficiently immersed that the partial exposurethereof is sealed by a portion of said bath, the bath being at atemperature sufficiently elevated to volatilize said material, creatingand maintaining a reduced oxygen atmosphere in a space in the thussealed retort above the level of said bath portion therein, maintainingsaid immersion for a time period sufficient to cause volatilization ofsaid coating material and escape of its volatilization product to saidspace, and voiding the escaped product from said space prior to removingthe object from the retort.
 3. The method of claim 2, in which thevolatilization product is voided under a condition of partial vacuum. 4.A method of removing coating material from an object, comprisingimmersing said object in a molten volatilization bath, creating andmaintaining a reduced oxygen atmosphere in a space above the level ofthe bath, which space is sealed against entry of external air theretowhen said object is so immersed, maintaining said immersion for a timeperiod and at an elevated temperature sufficient to cause volatilizationof said coating material and escape of the volatilization product tosaid space, and withdrawing the escaped product from the space in whichthe immersed object is disposed in a retort which is also at leastpartially immersed in the volatilization bath, being filled to apredetermined level with a portion of the bath in which the object isimmersed, the sealed space being in said retort and above saidpredetermined level therein.
 5. The method of claim 1, in which saidreduced oxygen atmosphere is created by placing said sealed space undera substantIally sub-atmospheric pressure.
 6. The method of claim 2, inwhich said reduced oxygen atmosphere in the retort is created by placingsaid sealed space in the latter under a substantially sub-atmosphericpressure.
 7. The method of claim 4, in which said reduced oxygenatmosphere in the retort is created by placing said sealed space in thelatter under a substantially sub-atmospheric pressure.
 8. The method ofclaim 2, in which said reduced oxygen atmosphere in the retort iscreated by introducing a normally substantially non-oxidizing gas intosaid sealed space of the retort.
 9. The method of claim 4, in which saidreduced oxygen atmosphere in the retort is created by introducing anormally substantially non-oxidizing gas into said sealed space of theretort.
 10. The method of claim 1, in which the object is suspendedduring the volatilizing immersion thereof in said retort portion of saidbath.
 11. The method of claim 2, in which the object is suspended duringthe volatilizing immersion thereof in said retort portion of said bath.12. The method of claim 4, in which the object is suspended during thevolatilizing immersion thereof in the retort portion of said bath. 13.The method of claim 2, in which said bath portion enters the retort fromthe bottom of the latter as the object and retort become immersed, saidsealed retort space to which the volatilization product escapes being atthe top of the retort.
 14. The method of claim 4, in which said bathportion enters the retort from the bottom of the latter as the objectand retort become immersed, said sealed retort space to which thevolatilization product escapes being at the top of the retort.
 15. Themethod of claim 11, in which said bath portion enters the retort fromthe bottom of the latter as the object and retort become immersed, saidsealed retort space to which the volatilization product escapes being atthe top of the retort.
 16. The method of claim 12, in which said bathportion enters the retort from the bottom of the latter as the objectand retort become immersed, said sealed retort space to which thevolatilization product escapes being at the top of the retort. 17.Apparatus for removing by volatilization a coating material from anobject, comprising an object-receiving retort having means to seal theinterior thereof as at least partially immersed, along with an objectreceived therein, in a volatilizing bath, said retort having an exposedportion at which the bath enters the thus immersed retort, means formaintaining the bath at a temperature sufficiently elevated tovolatilize said material, means for creating a reduced oxygen atmospherein a space of the retort above the bath portion therein, thevolatilization product escaping to said space, and means for voidingsaid product from said space after volatilization.
 18. The apparatus ofclaim 17, in which said retort has an open bottom affording said closedportion, and means sealing the top of the retort above the level of thebath entering the same.
 19. The apparatus of claim 17, in which saidretort has an open bottom affording said closed portion, and meansreleasably sealing the top of the retort above the level of the bathentering the same.
 20. The apparatus of claim 19, in which said sealingmeans is a cover removable from the remainder of the retort before andafter volatilization, the cover being provided with a fitting-typeconnection assisting in the creation of said reduced oxygen atmosphere.21. The apparatus of claim 17, in which said retort has means forlowering and raising the same relative to the bath respectively beforeand after immersion of the retort.
 22. The apparatus of claim 19, inwhich said retort has means for lowering and raising the same relativeto the bath respectively before and after immersion of the retort. 23.The apparatus of claim 17, in which said retort is in fixed relation tothe bath before, during and after immersion thereof.
 24. A method oftreatIng an object to separate organic and inorganic materials thereofas subjected to treatment, comprising immersing said object in a moltenvolatilization bath, creating and maintaining a reduced oxygenatmosphere in a space above the level of the bath by evacuating saidspace, which space is sealed against entry of external air thereto whensaid object is so immersed, maintaining said immersion for a time periodand at an elevated temperature sufficient to cause volatilization of theorganic material, escape of the organic volatilization product to saidspace and said separation of said materials, and withdrawing the escapedproduct from the space.
 25. Apparatus for treating an object to separateorganic and inorganic materials thereof as subjected to treatment,comprising an object-receiving retort having means to seal the interiorthereof as thus subjected, along with an object therein, to avolatilizing environment, means for maintaining said environment at atemperature sufficiently elevated to volatilize said organic material, avacuum pump for creating a reduced oxygen atmosphere in a space of theretort adjoining said atmosphere, the gaseous product of the organicmaterial escaping to said space, and means for voiding said product fromsaid space.
 26. Apparatus for treating an object to separate organic andinorganic materials thereof as subjected to treatment, comprising anobject-receiving retort having means to seal the interior thereof as atleast partially immersed, along with an object therein, in avolatilizing bath, means for maintaining said bath at a temperaturesufficiently elevated to volatilize said organic material, means forcreating a reduced oxygen atmosphere in a space of the retort above thebath therein, the gaseous product of the organic material separatingfrom the inorganic material and escaping to said space, and means forvoiding said product from said space.